One deviation from this ideal system is mathematically described by an equation that includes a term
 proportional to the cub
One deviation from this ideal system is mathematically described by an equation that includes a term
 proportional to the cube of position, where the proportionality constant is less than zero in the "soft" case.
 That equation is the Duffing equation. Another deviation from this ideal system is mathematically
 described by an equal that includes a term proportional to the time derivative of position, where the
 proportionality constant is known as the damping coefficient. This system itself is described by a
 second-order differential equation formed by equating Newton's Second Law and Hooke's Law. For 10
 points, sinusoidal motion is typical of what kind of system exemplified by pendulums and
 masses-on-springs?
One deviation from this ideal system is mathematically described by an equation that includes a term
 proportional to the cube of position, where the proportionality constant is less than zero in the "soft" case.
 
simple {harmonic} oscillator [or {SHO}; or simple {harmonic} motion; or {SHM}; or {mass}-{on}-{a}-